1. Field of the Invention
The present invention relates to a service coupling for use in directing refrigerant from a refrigerant supply source to a refrigeration system through a charging port which is normally attached to the refrigeration system and in communication therewith. The service coupling may also be used to evacuate refrigerant from a refrigeration system.
2. Description of the Related Art
Traditional refrigerants, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), are strictly regulated because of their contribution to the depletion of ozone in the atmosphere. The search for new and environmentally benign refrigerants to replace the existing CFCs and HCFCs led to the introduction of hydrofluorocarbons (HFCs), such as R134a. However, HFCs still exhibit a relatively high global-warming potential (GWP) and higher usage costs as compared to natural refrigerants, such as carbon dioxide and ammonia. These concerns have spurred calls for the investigation of alternative refrigeration systems employing refrigerants other than HFCs. The automotive air-conditioning industry has already begun to address the challenges of replacing HFCs, through the development of refrigeration systems employing carbon dioxide as the refrigerant.
Service couplings or adapters used to direct refrigerant from a refrigerant supply source to a refrigeration system through an inlet or xe2x80x9cchargingxe2x80x9d port in the refrigeration system, are well known in the art. One known service coupling employs one or more features that allow for a xe2x80x9cquick connectxe2x80x9d to the charging port of the refrigeration system. Once connected, a service valve in the service coupling engages and actuates a port valve in the charging port to open a refrigerant flow path between the charging port and the service coupling. The service valve is typically moved into engagement with the port valve by a rotatable knob that is threadably connected to the service coupling.
Conventional service couplings, such as those used to service automotive R134a air-conditioning systems, are generally designed to function at pressures up to approximately 100 psi (6.9 bar). However, refrigeration systems employing carbon dioxide as the refrigerant typically operate at pressures significantly higher than typical R134a refrigeration systems, i.e., greater than 100 psi (6.9 bar).
Due to these relatively high pressures, conventional service couplings suffer from several limitations that generally preclude their use in refrigeration systems employing carbon dioxide. One limitation is that the relatively high refrigerant pressure applies a significant load on the service valve, thereby requiring an excessive amount of torque to turn the knob.
Another limitation is that the xe2x80x9cquick connectxe2x80x9d features of the service coupling are rendered virtually inoperable due to entrapped pressurized refrigerant between the service coupling and charging port prior to disconnection. This trapped pressure also causes an undesirable violent disconnection of the service coupling from the charging port.
Still another limitation is that the refrigerant flow rate through a conventional service coupling during evacuation of a refrigeration system is relatively high. In a refrigeration system employing carbon dioxide as the refrigerant, a relatively high evacuation flow rate may cause explosive decompression of the seals, i.e., the undesirable rapid expansion of gaseous refrigerant trapped in a seal. A relatively high evacuation flow rate may also lead to the formation of xe2x80x9cdry icexe2x80x9d in the charging port or service coupling, which could prevent re-sealing of the service and port valves and allow the refrigerant to escape.
Therefore an improved service coupling is required for charging and evacuating relatively high-pressure refrigerant systems, such as those employing carbon dioxide.
A service coupling is provided for connecting a refrigerant supply source to a refrigeration system having an charging port that includes an axially displaceable port valve. The service coupling includes a body portion having a central passageway extending along an axis from an adjustment end to an outlet end and a lateral port positioned between the ends providing communication between the central passageway and the refrigerant source. An axially moveable valve housing is disposed in the central passageway. The valve housing extends from a first end positioned between the lateral port and the outlet end and a second end positioned proximate the adjustment end. The valve housing includes at least one pressure balancing passage that extends therethrough from the first end to the second end, and a service valve sealingly engaged within the valve housing. An actuator is provided to move the valve housing from a rearward position toward the adjustment end to a forward position toward the outlet end. Axial movement of the valve housing to the forward position causes the service valve to abut and disengage the port valve from sealing engagement in the charging port and the service valve from sealing engagement in the valve housing to open a refrigerant flow path. Axial movement of the valve housing to the forward position also creates a void between the second end of the valve housing and the body portion. The void is provided in communication with the refrigerant flow path by the at least one passage that extends through the valve housing, such that the pressure is substantially balanced on either end of the valve housing. The balance of pressure on either side of the valve housing results in only a minimum amount of force being required to move the valve housing within the central passageway.
In another embodiment of the present invention, the service coupling is provided with at least one bleed passage for venting pressurized refrigerant trapped between the service coupling and the charging port prior to disconnection. Movement of the valve housing to the forward position seals the bleed passage, whereas movement of the valve housing to the rearward position closes the flow path and permits the residual refrigerant trapped between charging port and service coupling to be released through the unsealed bleed passage.
In yet another embodiment of the present invention, the lateral port is provided with a coupling member for connecting the service coupling to a refrigerant supply/evacuation system. The coupling member includes a check valve or restrictor that is configured to restrict refrigerant flow through the lateral port in a first direction and to permit substantially unrestricted refrigerant flow through the lateral port in a second direction opposite the first direction.
Among other advantages, the novel design of the inventive service coupling permits a refrigerant flow path to be opened between the charging port of a relatively high-pressure system and the service coupling with minimal effort. Another advantage is that the refrigerant trapped between the charging port and the service coupling is automatically vented after closing of the service valve and port valve, permitting an easy and relatively non-violent disconnection of the service coupling from the charging port. Still another advantage is that the flow rate of the refrigerant being evacuated from the refrigerant system is readily controlled by the check valve to minimize the occurrence of explosive decompression or the formation of dry ice.
Various additional aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.